Acomposite plane wall consists of a 5-in.-thick layer of insulation (ks = 0.029 btu/h*ft*°r) and a 0.75-in.-thick layer of siding (ks = 0.058 btu/h*ft*°r). the inner temperature of the insulation is 67°f. the outer temperature of the siding is -8°f.
determine at steady state:
(a) the temperature at the interface of the two layers, in °f, and (b) the rate of heat transfer through the wall in btu/h*ft^2 of surface area.

An external consultant recommends that a plant installs a bank of capacitors for power factor correction. this will reduce the peak electrical demand charges by an average of 93 kw every month. the plant current pays $13 per kw in peak demand charges. the capacitor bank will include 223 kw of fixed capacitors, and 183 of variable capacitors. the fixed capacitors cost $59 per kw, and the variable capacitors will cost $65 per kw. the consultant charges 21% of the equipment costs to install the capacitors. because this project will reduce the demand for the electric utility, they are prepared to provide a one-time rebate of $42 per kw of reduced demand. what is the simple payback period for this project (in years)?